1. Field of the Invention
The present invention relates to a planarity measuring roller constructed as a loop lifter which is adjustable relative to a rolled strip. The loop lifter includes a plurality of measuring zones located next to one another over the width of the rolled strip. Each measuring zone includes a rotatably mounted individual measuring roller which is pivotable in a clockwise direction and interacts with a force measuring device.
2. Description of the Related Art
A loop lifter of the above-described type was disclosed in DE-C2 40 31 666 as a control element for controlling the strip tension in strip rolling mills. The strip should preferably be without tension, i.e., a corresponding control variable should be zero. The loop lifter serving as a control element for controlling the strip tension is arranged, for example, at the exit side of a roll stand. The loop lifter has a plurality of measuring rockers arranged in pairs and distributed over the width of the loop lifter, wherein each measuring rocker has on one side a measuring roller facing the strip and a force measuring element on the other side.
In principle, the loop lifter or its individual measuring zones are constructed like a scale. Always two plate-shaped measuring rockers arranged parallel next to each other at a distance receive a measuring roller and have a pivot bearing screwed to a guide plate. Arranged additionally underneath the pivot bearing is a rotary axis for a height correction arm; this height correction arm is adjusted by several screws in such a way that the measuring roller is in a horizontal position. Each measuring roller is provided with two force measuring elements, wherein one force measuring element is provided at the measuring rocker and the other force measuring element is provided at a height correction arm. The height correction screws simultaneously constitute means for securing against lifting off. The configuration of the measuring zones of this known loop lifter make it necessary that the measuring roller has a degree of freedom in the horizontal plane. This is achieved by a cantilevered mounting by means of spherical roller bearings which are each arranged on an axis of the measuring rockers.
The two measuring rocker plates supporting each measuring roller have only a low stiffness in transverse direction, so that an appropriately large free space must remain between the individual measuring zones or measuring rocker plate pairs in order to prevent the plates from contacting each other. Because of the low stiffness of the measuring rocker plates and the cantilevered mounting of the measuring roller, there is the danger that the measuring rollers will be deflected out of the horizontal in the case of an eccentric load and that, as a result, the rolled strip is damaged by the raised roller edge on one side. When the measuring roller is inclined in this manner, there may also occur a contact with the measuring rocker which would lead to damage.
In this connection, especially endangered are the lubricant supply lines to the measuring roller bearings a damage of which would result in a failure of the bearing function. Finally, the friction resulting from a contact of the measuring rocker by the measuring roller would falsify the measurement. Furthermore, this loop lifter has many individual components which additionally must be mounted so as to be rotatable and, consequently, require a complicated lubrication. Also, the measuring rollers must not only be aligned in a time-consuming manner by means of many counterscrews and adjustment screws, but they must also be readjusted very frequently because they become loose or separated by the external loads and vibrations.